Production of ferrocyanids from gas.



warren srn'rjns Parana oisr rc WALTHER 'FELD, or HONNITNGEN-ONEHE-RHINE, GERMANY.

PRODUCTION OF FERRocYANiDsFRom GAS.

Specification of Letters Patent.

Patented Oct. 2, 1906.

Application filed May 1,1906. Serial No. 314,699.

To (tZZ- Hi/b07771 it may concern:

Be it known-that I, WALTHER FELD, a sub j eot of the King of Prussia, German Emperor,

residing in Honningen-on-theRhine, Kingdom of Prussia, German Empire, have invented certain new and useful Improvements in the Production of Ferrocyanids from Cyanogen Contained in Gases, of whichithe following is a specification. 3. I

In order to obtain ferrocyanids from the cyanogen in coal-gases and the like, such gas has been treated with a suspension or solution of an iron compound, together with a basic substance, such as alkali, earth alkali, magnesia, or ammonia. In some cases the ammonia present in the gas has been used as the basic substance with or without the addition of a salt solution to the iron compound. The gases as a rule contain sulfureted hydrogen, by which the iron ccmpoundis converted into suliid ofiron. The absorption of hydrocyanic acid by sulfid of iron in the pres ence of a basic substance is slow and incomplete, as such absorption is a secondary reactlon, as shown in the follo wing equation:

cyanogen in the molecular proportion of one to two, respectively, as indicated by the formula Fe ((JN I have now found that the conversion of the iron compound employed into sulfid of iron is avoided by treating the iron compound with a ferrocyanid of an alkali, an earth alkali, magnesia, or ammonia before the said iron compound comes into contact with the gas to be treated.

In using ferrous sulfate as the iron compound and ferrocyanid of calcium for its precipitation g sum and ferrous cyanid are formed. If fife gas be treated with this ferprecipitate the ferrous cyanid and lime is the basic substance employed; but it is to be un' derstood that I do not limit myself to the use of these substances. The ferrous chlorid is dissolved in water, and to this solution is added sufficient calcium ferrocyanid to p'recipitate all the ferrous chlorid from the solu-. .tion. To two molecular proportions of ferrous chlori d nearly one molecular proportion of calcium ferrocyanid is used; but anexcess of calcium ferrocyanid does not interfere with the process. Insoluble. ferrous cyamd and soluble calcium chlorid are formed. The cal cium ferrocyanid solution may be added to the ferrous chlorid or the ferrous chloridmay be added to the calcium-ferrocyanid solution. The liquor thus prepared is mixed. with at least two molecular proportions of lime for each molecular proportion of ferrous chlorid. The basic substance may be added to either solution either before or after the precipitation of ferrous cyanid. with this liquor hydrocyanic acid isabsorbed according to the following equation:

gas, some insoluble ammonium-calcium ferlocyanid is formed; but this formation 1s less in proportion as the heat .under which the reaction is carried on is greater.

Instead of using a ferrocyanid salt to precipitate ferrous cyanid the liquor which has already been used for treating gas and which contains ferrocyanid in the required form can be used for precipitation. If the liquor containing the ferrous cyanid should be too dilute, it may be separated from ferrous cy- In treating'tlfe gas loo anid by filtration'and the ferrous "cyani'd be mixed with Water or milk of limetin the required proportion before us'ing'it'itotTeat'the I claim as my invention' 1. The process of obtaining ferrocyanids which consists in treating a gas containing hydrocyanic acid and sulfureted hydrogen with an iron compound to which a basic substance is added and from W111 ch before bringing the compound in contact With the gas, ferrous cyanid is precipitated by treating with a'ferrocyanid salt. v

2. The process of obtaining ferrocyanids which consists in treating a gas containing stanceis added andfromwhich before bringing in contact with the gas ferrous cyanid is "precipitated by treating with a liquor from which ferrous cyanid has previously been preeipi'tatedbytreatment W ith a ferro'cyanid salt.- In testimony whereof I have signed this specification in the presence of two subscribing Witnesses.

WALT-HER FEED;

WVitnesses: I

WOLDEMAR HAUPT, HENR *HASPER. 

